title: Tidal expiratory flow limitation at rest as a functional marker of pulmonary emphysema in moderate-to-severe COPD.
abstract: BACKGROUND
  Tidal expiratory flow limitation (EFL) is a step of paramount importance in the functional decline in COPD. Among mechanisms contributing to EFL, loss of airway-parenchymal interdependence could mostly be involved.
  
  
  OBJECTIVE
  To assess if EFL is a functional marker more frequently linked to prevalent pulmonary emphysema rather than to prevalent chronic bronchiolitis in COPD patients with moderate-to-severe airflow obstruction.
  
  
  METHODS
  Forty consecutive stable COPD patients with FEV1 between 59 and 30% of predicted were functionally evaluated by measuring spirometry, maximal flow-volume curve and lung diffusion capacity (DLCO) and coefficient of diffusion (KCO). EFL was assessed by the negative expiratory pressure (NEP) method both in sitting and supine position. Chronic dyspnea was also scored by modified Medical Research Council (mMRC) scale.
  
  
  RESULTS
  In sitting position 13 patients (33%) were flow limited (FL) and 27 were non-flow limited (NFL). Only FEV1/FVC, FEV1 and MEF25-75% were different between FL and NFL patients (p < 0.01). In supine position, however, among NFL patients in sitting position those who developed EFL, had significantly lower values of DLCO and KCO (p < 0.05) and higher mMRC score (p < 0.01), but similar values of FEV1 as compared to those who did not have EFL.
  
  
  CONCLUSIONS
  In COPD EFL in sitting position is highly dependent by the severity of airflow obstruction. In contrast, the occurrence of EFL in supine position is associated with worse DLCO and KCO and greater chronic dyspnea, reflecting a prevalent emphysematous phenotype in moderate-to-severe COPD patients.
authors.affiliation: 1Unit of Respiratory Medicine, Department of Medical and Surgical Sciences, University of Brescia , Brescia , Italy.
authors.forename: Stefania
authors.initials: S
authors.lastname: Chiari
authors.forename: Sonia
authors.initials: S
authors.lastname: Bassini
authors.forename: Alessia
authors.initials: A
authors.lastname: Braghini
authors.forename: Luciano
authors.initials: L
authors.lastname: Corda
authors.forename: Enrico
authors.initials: E
authors.lastname: Boni
authors.forename: Claudio
authors.initials: C
authors.lastname: Tantucci
mesh_terms: D000368:Aged; D001988:Bronchiolitis / Q000503:physiopathology*; D029481:Bronchitis, Chronic / Q000503:physiopathology*; D015331:Cohort Studies; D005260:Female; D005541:Forced Expiratory Volume; D006801:Humans; D008168:Lung / Q000503:physiopathology*; D008297:Male; D008875:Middle Aged; D029424:Pulmonary Disease, Chronic Obstructive / Q000503:physiopathology; D011656:Pulmonary Emphysema / Q000503:physiopathology*; D012123:Pulmonary Ventilation; D012129:Respiratory Function Tests; D012720:Severity of Illness Index; D013990:Tidal Volume